It is known that organic and polymeric materials with large delocalized .pi.-electron systems can exhibit nonlinear optical response, which in many cases is a much larger response than by inorganic substrates.
In addition, the properties of organic and polymeric materials can be varied to optimize other desirable properties, such as mechanical and thermoxidative stability and high laser damage threshold, with preservation of the electronic interactions responsible for nonlinear optical effects.
Thin films of organic or polymeric materials with large second order nonlinearities in combination with silicon-based electronic circuitry have potential as systems for laser modulation and deflection, information control in optical circuitry, and the like.
Other novel processes occurring through third order nonlinearity such as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have potential utility in such diverse fields as optical communications and integrated circuit fabrication.
Of particular importance for conjugated organic systems is the fact that the origin of the nonlinear effects is the polarization of the .pi.-electron cloud as opposed to displacement or rearrangement of nuclear coordinates found in inorganic materials.
Nonlinear optical properties of organic and polymeric materials was the subject of a symposium sponsored by the ACS division of Polymer Chemistry at the 18th meeting of the American Chemical Society, Sept. 1982. Papers presented at the meeting are published in ACS Symposium Series 233, American Chemical Society, Washington, D.C. 1983.
The above recited publications are incorporated herein by reference.
Of more specific interest with respect to the present invention embodiments is prior art relating to side chain liquid crystalline polymers, such as the five articles published on pages 275-368 of "Polymeric Liquid Crystals", edited by A. Blumstein (Plenum Publishing Corporation, New York, 1985).
U.S. Pat. No. 4,293,435 describes liquid crystalline polymers corresponding to the formula: ##STR2## where R.sub.1 is hydrogen or methyl, n is an integer from 1 to 6, and R.sub.3 represents a structural element containing at least two phenylene groups.
Makromol, 179, 2541(1978) by H. Finkelmann et al describes a model consideration for liquid crystalline polymers with biphenyl groups as mesogenic entities.
J. Polym. Sci., 19, 1427(1981) by Paleos et al describes the synthesis of liquid crystalline polymers which are prepared by the interaction of poly(acryloyl chloride) with mesoogenic compounds such as p-aminobiphenyl.
Eur. Polym. J., 18, 651(1982) describes comb-like liquid crystalline polymers of the smectic and nematic types with cyanobiphenyl groups in the side-chain: ##STR3## where R is hydrogen or methyl, n is an integer of 2-11, and X is an oxy, alkylene or carbonyloxy divalent radical.
Other publications which describe thermotropic liquid crystalline polymers with side chain induced crystallinity include Polymer, 25, 1342(1984); Eur. Polym. J., 21, No. 7, 645(1985); Polymer, 26, 615(1985); and references cited therein.
The above listed publications are incorporated herein by reference.
There is continuing interest in the theory and practice of liquid crystalline polymers which are characterized by an oriented state of comb-like side chain structures.
There is also an increasing research effort to develop new nonlinear optical organic systems for prospective novel phenomena and devices adapted for laser frequency conversion, information control in optical circuitry, light valves and optical switches. The potential utility of organic materials with large second order and third order nonlinearities for very high frequency application contrasts with the bandwidth limitations of conventional inorganic electrooptic materials.
Accordingly, it is an object of this invention to provide novel liquid crystalline polymers.
It is another object of this invention to provide thermotropic liquid crystalline polymers having mesogenic side chains which exhibit nonlinear optical response.
It is a further object of this invention to provide electrooptic light modulator devices with a transparent polymeric nonlinear optical component comprising a thermotropic side chain liquid crystalline polymer.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.